Space discharge tube



y 1, 1936. H. E. ACKMAN ET AL 2,047,944

SPACE DISCHARGE TUBE Filed April 25, 1935 2 Sheets-Sheet l .2? Tia-z INVENTORS ATTORNEY Jul 21, 1936.

H. E. ACKMAN ET AL SPACE DISCHARGE TUBE Filed April 25, 1935 2 Sheets-Sheet 2 INVENTORS ATTORNEY sr'rss ATJIENT OFFICE SPACE DISCHARGE TUBE Howard E. Ackman and Emmett Finley Carter, Emporium, Pa., assignors to Hygrade Sylvania Corporation, Salem, Mass, a corporation of Massachusetts Application April 25, 1935, Serial No; 18,115 17 Claims. (01. 250-275) A :This invention relates to space discharge tubes,

and. with particularity to an improved form of electrodev support for discharge devices having a filamentary member.

In certain types of space discharge tubes, such for example as electron discharge tubes ordinarily employed in radio receiving and transmitting apparatus, it is customary to provide means to support and space'a plurality of electrodes in such a way that the electrical and mechanical 7 characteristics are not disturbed by mechanical vibrations or the like. This is particularly true in-ithe case of those devices employing a filament w which is adapted to act either as a heater member oras an. electron emitter. In tubes employing a filament of V-shaped or similar configuration, means "are usually provided to maintain the filament taut, especially when the filament is at its relatively high operating temperature. Many methods of supporting such filaments have been proposed, but the most common one employs a tension hook or spring which engages the bight of the filament. -While these metallic spring supports .have advantages, nevertheless in certain types .of tubes the use of a. metal spring support for the filament, is undesirable. One of the most 7 serious draw-backs to the use of filament tensioning springs is the fact that when the filament is at its operating temperature the heat is unavoidably-conducted to the spring which, after a' period 'of use, tends to lose its resiliency and therefore its effectiveness in tensioning the filamen'tx: Another disadvantage of metal springs is that the filament hook must be of relatively small masswhere it engages the filament, thus necessitating a sharp-bend in the filament with the'consequent liability to rupture at thebend. A still further disadvantage of the metal'hook typeof filament support is that it is very difficult to provide a. spring or hook which is resilient along only: one axis, with the result that while 7 the filament may be kept under'the proper. tension longitudinally,it may vibrate bodily in a lateral direction thus changing the electrical characteristics of the tube. Added to these disadvantages is theliability to production of microphonic noisesby reason of the metal-to-metal contact between the filament and the metal hook, and the fact that the spring or book may have a natural period of vibration within a frequency range which is'detrimental to the operation of the tube.

Accordingly, one of the principal objects of this invention is to provide an improved means for supporting a heatable filamentary member whereby the above-noted and other disadvantages are overcome.

Another object of the invention is to provide a novel form of insulator spring member for resiliently supporting a filament or the like. 5

A feature of theinvention relates to an insulator member which serves the double purpose of accurately spacing a plurality of electrodes from each other while maintaining one of the electrodes under tension.

Anotherfeature relates to the means for supporting a filament in a space discharge tube so that the legs of the filament are uniformly spaced apart.

Another feature of the invention relates to an improved arrangement including a resilient hook for tensioning a filament and means for preventing the hook from twisting the filament out of its normal planar shape.

Other features and advantages not specifically enumerated will be apparent after a consideration of the following descriptions and the appended claims.

While the invention is of prime importance as applied to electron discharge devices such as radio tubes or the like, it will be understood that it is equally well applicable to other types of devices employing a heatable filament which is required to be kept under tension. Therefore, while the drawings show the invention embodied in one specific'type of radio tube structure, it will be understood that this is done merely for purposes of explanation and not by way of limitation.

In the drawings, Fig. 1 illustrates in vertical section a radio tube mount embodying features of the invention.

Fig. 2 is a top plan view of the mount of Fig. 1.

Fig. 3 illustrates a modification of the invention.

Figs. 4, 5 and 6 show another embodiment of the invention. I

Referring more particularly to Fig. 1, the numeral l represents in dotted outline one wellknown form of enclosing envelope such as is employed in present day radio tubes. The envelope is sealed-to a reentrant portion 2 terminating in a press 3 wherein are sealed the various lead-in and support wires 4 to In inclusive. Supported on the wires 4 and I0 is a tubular metal electrode l l, and supported on the Wires. 5 and 50 9 is a grid electrode comprising a pair of side rods l2, [3, around which is helically wound the fine grid wire I4 the individual turns of the wire I4 being fastened in any suitable manner to the siderods l2, I3;

side rods l2, it. The insulator discs may be held in place on the wires 4 and I by small lugs I8; welded to the said wires although any other siInilar methodof fastening the discs in place may be employed. The lower mica disc I6 is provided with a slot 19 to allow the filament "l vto pzass therethrough, while the upper mica disc [1, 'as' shown in Fig.2, is provided with an opening '20 and with an integral tongue 2l.- Tongue- H is preferably, although not necessarily, provided with tapered edges 22, 23 to impart the desired degree of. resiliency to the tongue. The forward: corners of the tongue 2| are/notched; asindi-z' catedby the numerals .24' and-25 tdprovide 'recesses'to receive the bighto'r bend zeofithe filamentsl'fii. Preferably the: notches 2'4 andi-25-are provided in alignment with'the perforationsin the disc 11' so: that when the filamentembraces the tongue 21', it is in planar alignment with the wires 4,10; l2, l3; Preferably thefilamentili is so" bent that the width of the bight. issubstantially.

thesame as; the width of the notched portion of tongue 21. With this arrangement. the fila-- ment may be kept under the desireddegree of the longitudinal tension because of the cantilever. 'spring action of the tongue 21'. However',.the -filament is prevented fromswayingi or vibrating'iniai lateral" direction because of p the. substantial lat .l eral rigidity of thetongue 2|. While, in order to facilitate assembly,- it is preferred to provide the forward end of the'tongue 21 with' oppositely disposed notches- 24, 25; to receive the filament bight, if desired -thetongue'21 may beprovided: with oppositely disposed slots or perforations:

through which the opposite legs ofthefilament pass- However, it hasbeen' found that if the lat-i 'eral edges of the notches 2'4" and: 2 5 are slightly inclined as shownin- Fig; 2, it is not necessary to employ slotsor perforations-to maintain the filament in position. If the'mica disc l l isof'too great a thickness to provide the required d'egree of resiliency to the tongue 2 l jthis tonguemay be scored or otherwise weakened as indicated by the dotted line 21 It will thusbe apparentthat because of the relatively large area of the tongue'2 l considerable damping eifect' 'is-pr'ovided' to off-set any tendency of the filament to vibrate-mime phonically and the tongue 2i may be' designed so that its natural period of vibratior rwillbe lower than any frequency which will be detrimental to the operation of the tube. '4

It will be understood of course that while the inve tion has been described in connectionwith an inverted U or V shape filament any other wellknown form offila'ment may likewise be-support'edby the disc H {and furthermore While a tube of the three element type" as-shown; it will be understood that a-[greater or less number of electrodes-may be *employed. Furthermore whilethe" drawings show theton'gue '2! as-supporting a filarnent ofthe coated type, itwill be'understoodj that the? invention; if desired; maybe employed in supportin the heater wires-{ of so-called indirect-lyheated cathodes. Itwill also be understood -tliat l thernethod of supporting the various' electrodes from the press of Fig. 1 is merely illustrative and and 2. For the purpose of simplicity the remaina atongue 54 similar. tothe tongue 2i of'Figsz'l that any other well known manner of support may be employed.

In certain cases it may be desirable to support r thefilament so that the side legs thereof aresubstantially parallel. Thus as illustrated in Fig. 3 the filament I5 is supported at its upper end by means of an insulator disc 28v having a notched V tongue 29 similar to the tongue 2| of Figs; 1 and 2.

The lower disc 30 instead 'of being provided with acrslot like the slot IQ of Fig. 1, is provided with 1 atongue 3! similar to'the tongue 29. 'In this embodiment the free-ends of the filament l5 are preferablyfastened to the support wires 6 and 8 so that thelower portions of the filament legs are in engagement with the edges of the notched portions 32 and 33 which notches correspond to -the notches 34, 35' in the top disc 28 and also to the notches' 24' and -01" the upper disc of Figs. 1

ing electrode or electrodes of the tube and the remaining: parts of the mount arejomittedfrom Fig. 3-11: beingunderstoodof coursethat the discs" .2 8 and 'aresupported' in $15 aced relation to? other in any well known mannerl In certain 'instancesit may bev preferableto empl'dy'the tongued mica above described merely for' the purpose of spacing: the'legs of the fila-- ment apart while employing an ordinary-resilient: metallic: hook to maintain the filament-taut Thus there is'shown in Fig.4. a preferred form oftube structure which has" been found" to prof-i V ducethei desi'red results. In this fi'gure the un meral36 indicates .in dotted outline; 50119 welt? knownform of enclosing bulb. having integrally" ing in the press 38. Sealed into the press 38 .are

the lead-in: and support. wires 39' to*46 inclusive. Fastenedto the wires SS'and? 43" a tubular metal? plate or anode M which may-be cylindrical in shape.- Mounted adjacent the upper and lovler llfi edges'of the'anode 41: are insulator discs" #83148! of mica; or other suitable: insulating-materials These discs may be held in pla'ce 'against'the"edges1 of. the anode by suitable lugsor swaged'portions- Won: the' wires- 39" and. 43a The. discs- H8 and? may be of any desired shape but are'preferabl'yfi attached thereto a reentrant' stem 31*terminatt-23a both ofth'e same shape as shownin Fig.5 of thei slot? through? which pass the two: legs of the: filament 5|; 'The free ends of theffilamen't are- 'welded to-the filament support wires 4 I, 46 while thefilament. is maintained undercvertical: terr- I drawings; The'lower disc-49ris provided witlr'a sion by'means-of a resilient metal hook 52: which may be welded to theupper end' 53"bf' thesup-' portiwire'dz as shown in detail in l 'igeflc For the purpose' of: spacing. the upper portion ofthe V filamentllegsz apart, an'd for insuring that: the

hdok 52 does not distort" the filament out ofitsi plan'an' s'hape, theupper' disc-48="is provided with T andfl2. InZ this embodiment however thetongue' 54 is: not re'lie'd upon to provide the tension fo'r the filament"; butis 'used merely to'sp ac'e the'legsir:

of the filament apart and to prevent' the'hoolc while it is under tension. It has been found how ever, that by interposing the mica tongue ii l'be tw e'en thefilament and the hook the saidho'ok canbe maintained-at a sufficiently'low' tempera=-'- ture to prevent its losing its springiness. In the particular tube illustrated; the filament- '5 l' is surrounded by a series of grids 55, 56, 51 and Each: 'eftheseigrids may consist of "a'- pair of metal uprights around which is helically wound a fine grid wire-preferably' with eachof thegrid c from dist'ortingthe planar shapeof the filamentf wire turns welded or 'mechanically fastened-to the vertical support wires, and in'orde'r to insure the proper spacingofthe electrodes the-grid support wires register with corresponding'perfo- 1 rations in the discs 48, 49,as shown clearlyin Figs. 4 and 5- of the drawings. Interposed between the grid55 and the grid 56 are' a pairof metal strips-59, 66, these strips-beingunited at their lower ends by the metal strap 6| which is of lo' course curved so to clear the legs of the filament, and the remaining electrode support wires. The upper ends of the strips 59 and 60 register with corresponding slots in the upper disc 48 as shown clearly in Fig. 5 of the drawings. When 15 the device of Fig. 4 is to be used as a frequency converter or oscillator modulator, the filament or cathode 5| in conjunction with the grid 55 and the strips 59 and 66 may form together with a suitable feed-back circuit arrangement (not I shown) an oscillator, so that the potential of grid 55 varies in a regular manner at the desired frequency under control of the oscillatory circuit. The grid 56 may have a suitable positive potential impressed thereon with respect to the filament or cathode so that it acts as an accelerating grid for the electrons emitted from the cathode. In effect therefore the grid 56 may be considered as the virtual cathode for the remaining electrodes of the tube, that is for the grid 51, grid 58 and the main anode 41. When the device is used for a frequency converter or oscillator modulator, the grid 5'! may be considered as the control grid in the sense that it modulates the electron stream from the virtual cathode formed by the grid 56 as described above and for this purpose a separate lead-in wire 62 may connect the control grid 51 preferably with the metal top cap 63. The grid 58 may be connected by the strap 64 to the accelerating or virtual cathode grid 56 and when a suitable positive potential is applied to the grid 58, it will act as a screen or shield grid to screen the control grid 51 from the fluctuations of potential on the anode 41.

While the embodiment of Figs. 4, 5 and 6 shows the tongued mica in a tube of the pentagrid type, it will be understood that it can be equally well applied to any other type of tube employing a filamentary heater or cathode.

Various changes and modifications may be made in the particular embodiments disclosed without departing from the spirit and scope of the invention.

What is claimed is:

1. In a device of the character described, a filamentary member, means to anchor said member at one end, and means to support said member resiliently at the other end, the last mentioned means including a flexible tongue consisting of insulation material and engaging said filamentary member. 7

2. In a device of the character described, a pair of filament sections, means to anchor said filament sections at one end, and means to support said sections resiliently at the other end, the last mentioned means including a flexible fiat tongue consisting entirely of insulation.

3. In a. device of the character described, a filament, means to anchor said filament at one end, and means to support said filament resiliently at the other end, the last mentioned means including an insulator strip provided with a cutout portion and a flexible tongue of insulation associated with said cut-out portion.

4. In a device of the character described, a. filamentary member, means to anchor said memher at one end, and means to support said member resiliently at "the other end, the last mentioned means including a fiat tongue of insulation flexibl'y supported at one end'and having at its other 5' end cut-out portions in its edges to' form a pair of oppositely'disposed notches to receive the fila-'- ment a device'of the character described, a fila ment and means for maintaining the filament 10 under tension comprising a mica tongue flexibly supported at one end, and having a filament engaging portion at the opposite end.

6. In a device of the character described a filament, an electrode cooperating with said filament, 15

an insulator spacer disc for insulatingly spacing said filament and electrode, said disc having a cut-out portion to form a free-ended insulator tongue to engage the filament to maintain it in vertical alignment. 20

7. In a device of the character described a filament having a bight, an electrode cooperating with said filament, a disc of insulation supported adjacent the bight of said filament and the end of the electrode, said disc having a cut-out portion 25 defining a flat tongue, said tongue having a plurality of notches to engage the filament bight.

8. In a device of the character described a filament, an electrode surrounding said filament, means to support said filament and electrode at 30 one end, insulator spacer means for spacing the filament from the electrode at the other end, said spacer means having an opening to receive the filament and being provided with an integral flexible tongue of flexible insulation in said open- 35 ing and engaging the filament to maintain it in axial alignment with said electrode.

9. A tensioning device for a filamentary electrode having a bight comprising a tongue of insulation flexibly supported at one end and having 40 its other end cut-out to form a pair of notches to receive the legs of the filament adjacent the bight thereof.

10. A combined electrode spacer and filament aligning member for space discharge tubes com- 45 prising a disc of insulation having a cut-out portion to receive a filament bight and having perforations to receive electrode support rods, said cut-out portion being provided with a struck out portion to form an integral flexible tongue of in- 50 sulation to engage the filament adjacent the bight thereof.

11. A combined electrode spacer and filament aligning member for space discharge tubes comprising a mica disc having a portion struck out 5 therefrom forming an integral fiat tongue, said tongue having a portion adapted to engage the bight of the filament.

12. A combined electrode spacer and filament tensioning member for space discharge tubes 'com- 60 prising a disc of mica provided with a cut-out central portion, a plurality of aligned perforations to receive electrode support rods, a flat resilient tongue in said opening said tongue being provided with notches in alignment with said perforations 6 said notches adapted to receive the filament.

13. A filament tensioning member for electron discharge tubes comprising a mica tongue having appreciable flexibility in the direction in which the filament is to be tensioned and being substantially rigid in a. transverse direction.

14. In a device of the character described a pair of filament sections having a bight portion, and means to space said filament sections and to maintain them under tension, said means includh1g2. mica tongueinserted between, the sections, of the filament adjacent the bightto maintai saidsections inn-planar n t.

, 15. A- device according to claim 1.4 in which the tongue is integrally formed from acut out portion of an insulator member which serves to space the filament sections from the remaining electrodes of a device, and the tension device-in the form of a spring hook engages the filament w bight. 1 t l J .16. An electrode spacer member for radio tubes gems.

comprisingra disc of rinsulation hayinga central struck out portion to provide an integral filament-- alignment tongue, and having a. plurality of pe17-' HOWARD, EQ A CKMANQ m EMMETT' F. CARTER. I 1 

